Hide in Menu, but show in Content

I have a Content site called "Accordion Holder" where all its subpages are listet as an accordion.
This works fine. But the subpages are also shown in the menu where I don´t want them to be shown.
If I activate the checkbox "Hide in menu" they disappear on BOTH - the menu AND on the "Accordion Holder" site.

Of course I could hide the second menu in general, but there are other pages where i do need the second menu level to be shown.
Has anyone a solution for this problem?